may any one help me plz in this exercise
A 50-mg dose of a drug is administered by rapid injection to a patient. The half-life of the drug is 9 hours.
a. find a model for the amount of drug in the bloodstream t hours after the drug is administered.

Question

may any one help me plz in this exercise 
A 50-mg dose of a drug is administered by rapid injection to a patient. The half-life of the drug is 9 hours. 
a. find a model for the amount of drug in the bloodstream t hours after the drug is administered.

rogue · Answer

$$F(t) = A e^{-kt}$$$$k = \frac {\ln 2}{t_{1/2}} = \frac {\ln 2}{9} \approx 0.07710635$$$$A = Initial Amount  = 50mg$$$$F(t) = 50 e^{-0.0771t}$$